[erlang-questions] Elevator demo

Håkan Huss huss01@REDACTED
Fri Jan 4 09:28:48 CET 2013

On Wed, Jan 2, 2013 at 6:14 PM, Francesco Cesarini
<francesco@REDACTED> wrote:
> The Elevator example was implemented by Hakan Huss in the late 90s at Erlang
> Systems. It was part of the 5-day Erlang Literacy course aimed at test and
> support staff of the GPRS project. It has been used to demonstrate how Quick
> Check can test elevator systems, and featured in a few academic papers.
> /F
I haven't looked at the code or the course material in the last ten
years, nor do I have it available in any readable format. (I may have
a course binder in a box somewhere in the attic, but I think I threw
away the floppies containing the course setup a couple of years ago
when I realized I didn't have a floppy disk reader any more :-) So all
of the following is very much IIRC.

Just to add a bit more of background: the elevator example was used as
a lab exercise in several parts of the course to practise different
topics such as behaviours, supervisors, release handling, etc. The
first exercise using the elevator example was the mentioned "bug" that
the elevator always stopped at every floor (it is actually not a bug,
but an elevator scheduler which is trivially guaranteed to fulfil the
requirements on elevator scheduling used in the example). Several
refinements of the scheduling were made in the course lab exercises.

Since the purpose of the exercise was to use many different aspects of
Erlang and OTP, the code has been written to use many behaviours
rather than to be the "best" solution for the problem. I still think
that the resulting architecture is pretty ok.


> On 31/12/2012 23:39, Loïc Hoguin wrote:
>> Hello 2013,
>> Just a quick link targeted mostly to people who teach Erlang or those who
>> want to demonstrate its features.
>> Last September Scott gave me the code he had for an old Ericsson elevator
>> training application that shows an application with a bug, and an upgrade
>> available to perform a release upgrade to fix the bug live. As these are
>> elevators, the bug (doors opening at every floor) can be quickly seen fixed
>> since the elevators will continue moving until their destination without the
>> bug triggering anymore once you did the upgrade.
>> You can find the source here:
>>   https://github.com/extend/elevators
>> It should work for R15. Probably does for R14 too, but I didn't test it.
>> As this is an old demo it uses gs, but I will port the code to wx for R16
>> once it is released if nobody did it before.
>> Patches are welcome. Also if you know more about the history behind this
>> application, I'm interested and will put these infos in the README file.
> --
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